CEO Exit Sets Microsoft on New Path

Steve Ballmer to Leave Within a Year; Stock Jumps 7%

In announcing his sudden retirement Friday after more than three decades at Microsoft Corp., Chief Executive Steve Ballmer will leave his successor with the enormous task of reviving one of the world's largest technology companies that finds itself beset by competitors on all fronts.

Mr. Ballmer, 57 years old, along with his college buddy and Microsoft founder Bill Gates, built the company into a profit machine whose Windows operating system will still power nearly all the 305 million personal computers expected to be...